Boost gas milage?

I've got a 96 GC with the 3.8 ltr engine. From the day I bought it (Oct 95) to today it has given me 18 to 23 mpg. I am wondering if anyone has tinkered with any systems to try to increase milage and what success you've had. I've heard of folks changing computer chips, intake ducting etc on other cars but, nothing specific to a GC. With the price of gas at $2.54 now and expectations of $3.00 /gal this summer, any milage increase would be a big plus.

What I did was installed a tornado air between the thottle body and aircleaner onto a 99 GC w/3.8L and went from avg of city/hwy 13/17 to 15/22. I installed it on another 97 T&C and they went from 18/24 to 24/26. Every little bit helps. lol. Getting ready to try running a K&N filter now as my cousin had decent success with his ford truck.